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great comet of 1882 when nearest the sun exhibited many of the lines ob-
tained in the laboratory from the vapors of sodium, iron, and magnesium
at the temperature of the Bunsen burner. As it receded the lines grad-
ually died out until a very few were left; and in the comet of 1886-7,
when last seen, all had died out except one line of magnesium. Thus
carbon also, which is such an important ingredient in organic life, appears
and disappears in cometary spectra according to the conditions of pressure
and temperature.

What Mr. Lockyer has done is to show that all the varied spectra and
classes of spectra, given out by suns, stars, nebulae, comets and shooting
stars, can be reproduced from actual meteorites which have fallen to the
earth, by experiments in the laboratory, with the exception only of those
of stars which, like Sirius, are glowing at a transcendental temperature
far exceeding that of our sun, and which cannot be approached by the
electric arc in any form of intense heat which can be obtained in our pres-
ent earth. Thus the " spectrum of the sun can be very fairly reproduced
(in some parts almost line for line) by taking a composite photograph of
the arc spectrum of several stony meteorites between iron meteoric poles."

We are now in a position to understand the meteorite theory of the
universe. Granted that the number of meteorites in space is practically in-
finite, and that they tend to coalesce into streams, their collisions supply an
equally unlimited fund of heat upon which we can draw at pleasure.
The amount of heat developed by each collision is the transformed energy
of the mechanical force. This force, and consequently this heat, in-
creases with the square of the velocity. Thus, if a tropical hurricane,
moving at the rate of 100 miles an hour, uproots trees and levels houses,
the same mass of air moving with the mean meteoric velocity of 33 1-2
miles per second, would exert a force of one hundred and forty-four mill-
ion times greater. We know from the explosion of dynamite that when a
gas expands very much quicker than the air can get out of its way, the
effect is as if the blow of a tremendous steam-hammer were inflicted on an



28 BEACON .LIGHTS OF SCIENCE.

nyielding anvil ; and we can readily conceive, therefore, how meteorites
are almost invariably burnt up and dissipated, even in the rare air of the
upper atmosphere, and how their repeated collisions in space might gen-
erate any required amount of heat

Suppose, therefore, in the beginning of things, space filled by an innu-
merable multitude of these little stony masses, composed of the one, oj
possibly two or three, primitive elements of matter, moving in all direc-
tions, with immense though different velocities, coalescing into stream*
and colliding, we have a basis out of which suns, stars, planets, satellites,
nebulae and comets might be formed. The looser aggregations, giving
fewer collisions and less heat, form comets and nebulae, and the clash of
two mighty streams gives us suns like Sirius in a state of intense lumi-
nosity and temperature. As these cool and contract by radiating out
their heat, they pass into the second stage of stars of which our sun is one,
still glowing with heat and light, but cooled down to a point at which
the primitivte elements can combine and form secondary ones, which can
be detected by the spectroscope, and identified with those with which we
are familiar as chemical elements upon earth. As cooling proceeds, they
pass from the white-hot into the red-hot stage, and finally into the cold
and lifeless non-luminous stage of burnt-out suns. Not, however, neces-
sarily to die, for in the chances of infinite time these dead and invisible
masses may collide together, and at a blow regain their youth, and com-
mence the cycle anew as suns of the first order.

There is grandeur in the idea which, to a certain extent, reproduces
what the kinetic theory of gases teaches as to the clash of innumerable
atoms darting about in all directions, producing the temperature and pres-
sure of a gas in a confined space. Only here, instead of atoms so small
that one of them is of the size of a rifle bullet, compared with the earth
we have stony masses for atoms, stars and nebulae for molecules, and in-
stead of glass jars or bladders, the whole universe.

This, however, is only the first stage of the theory. What are these lit-
tle stony bodies, and how did they come there ? The only answer we can
give is derived from the constitution of those larger meteor-stones which
actually fall on the earth and can be examined. They have invariably
the appearance of fragments torn from larger bodies by collisions or ex-
plosions, and there is no reason for doubting that what they appear to be
they are.

This carries us back to the impact theory of which a full account is
given in the work recently published by Dr. Croll on Stellar Evolution.
It supposes that for an almost infinite time, an almost indefinite number
of dark stars, or cold and non-luminous solid bodies of stellar magnitude,
have been rushing about in an unlimited space in all directions, and with
enormous velocities. Occasionally they collide, and, as mechanical
principles show, generate an intense heat, more than sufficient to convert
their whole mass into glowing gas, at a temperature which may possibly



PROBLEMS 01' THH FUTURE. 29

dissociate its atoms, with the exception of some fragments from the shat-
tered surfaces which are thrown off into space by the sudden generation
of explosive gas. That they really are such dark suns rushing through
space appears certain from what we know respecting the constitution of
the visible stars. We find them exhibiting all ranges of temperature, from
the intense heat of the white stars like Sirius, to that of the duller red stars
like Arcturus, our own sun occupying an intermediate position; while our
moon affords an example of a dead world, which from its smaller size has
cooled more rapidly. As the moon is, so must the red stars inevitably
become in a sufficient number of millions of years, if the laws of nature
continue uninterrupted. And their proper motions, rushing through space
in different directions with velocities ranging up to 400 miles per second,
must continue after they have become dark, as long as the first law of
motion holds good, that bodies in motion cannot generate changes of
motion of themselves, but must continue to move forwards in a-straight
line unless acted upon by some external force.

Among bodies thus rushing in different directions collisions must oc-
casionally occur, and it is a matter of simple calculation that the mechani-
cal force converted into heat by such collisions, is amply sufficient to pro-
duce any temperature that may be required to create new suns and nebulae,
and to account for all the phenomena which are actually observed.

Moreover, the existence of such dark bodies is established by direct
observation. That fragmentary masses, weighing several cwts, come in
from space and fall upon the earth is a fact. So also is it a fact that
bright stars, some of them like the famous new star in Cassiopaea,
brighter than stars of the first magnitude, suddenly blaze out and gradual-
ly disappear. The impact theory accounts for this, while the nebular
theory, or any hypothesis based solely on the contraction of a mass of
nebulous vapor under the law of gravity, entirely fails to do so. Again,
the phenomena of variable stars can best be explained by assuming either
that such stars pass periodically through dense streams of meteoric matter,
increasing their light, or else that large dark bodies are periodically inter-
posed between us and the stars, and thus diminish it The constitution
also of comets, and of many nebulae, as disclosed by the spectroscope, is
far better explained by the impact than by the nebular theory. In fact,
it is inconsistent with the latter theory, which can give no account of
comets, meteorites, or other phenomena, which imply small dissociated
portions of matter, moving in streams or aggregating in nebulae, and rush-
ing with immense velocities in paths inclined to each other at different
angles, and which have no relation to the rotating plane of the solar or
any other system. Even within the limits of the planetary system there
are many facts which are better explained by the theory of impact than by
that of contraction. For instance the great difference in the inclination
of the axes of rotation of many planets and satellites to the plane in
which they revolve about the sun and their primaries. But after all there



3 o BEACON LIGHTS OF SCIENCE.

is no real inconsistency between the impact theory and that of Laplace.
The former takes up the history of the universe at an earlier stage, and
upplies a mass of gas or cosmic matter, at a higher temperature, and with
that temperature longer maintained by repeated collisions and indraught
of meteorites, than is assigned to it by the nebular hypothesis, but ulti-
mately a great deal of this gas must resolve itself into such a medium as
Laplace supposes, contracting and forming whirls under the operation of
gravity. The triumphs of mathematical science deduced from Newton's
law of gravity were so signal, that it is not surprising that it should have
been assumed that gravity, and gravity alone, was the fundamental law
which would explain everything. But, as often happens, increasing
knowledge has rendered many things uncerta'n which appeared to be cer-
tain. Problems which seemed simple have become complex, and it has
become apparent that the universe contains many forms of motion, and
many manifestations of energy, which cannot be explained by the laws of
gravity. For instance, the runaway stars, the world of meteorites, the
proper motions of molecules and atoms, and the requisite duration of
solar heat to account for the undoubted facts of geology. The law of
gravity and the nebular theory were a great step towards reducing the
phenomena of the universe to one great uniform law; but the theory of
impact takes up the history at an earlier stage, and carries us one step
further towards infinity and eternity. If the whole stellar universe is not,
so to speak, the crop of a single season, but an indefinite succession of
crops, stars being born and dying, dying and being renewed, without ap-
pearance of a beginning or an end, the vista of existence is vastly en-
larged. But even this is not the last step towards the unknowable.
Granted that these dark suns are facts, they are not ultimate facts. They
are matter, and matter is made up of molecules, and molecules of atom*.
Judging from the fragments which reach the earth, and the teachings of
the spectroscope, meteoric matter is composed of a few atoms identical
with those which are the most common elements of terrestrial chemistry.
Hydrogen, nitrogen, sulphur, iron, nickel, calcium, silicon, and alum-
inium, are the principal, if not the sole constituents of meteoric stones,
and are those the lines of one or more of which appear in the spectra of
stars, nebulae, meteors, and comets, according to their conditions of tem-
perature and pressure. What then are these atoms ? There are some
seventy of them known to chemists as ultimate elements ; that is to say,
which are not further resolvable by any means available in our labora-
tories. But no one can suppose that this is really the ultimate fact, and
that original matter really consists of seventy indivisible units, ranging in
weight from the i of hydrogen to the 240 of uranium, and more than hatf
of them consisting of exceedingly rare elements, which play no apprecia-
ble part in the construction of any form of matter. The mind refuses to
accept the conclusion that such little mole-hills as yttrium, zirconium and
gallium, only known as minute products of a few of the rarest minerals,



PROBLEMS OF THE FUTURE. 31

really present unsurmountable obstacles to the science which has scaled
Alps, measured light-waves, and weighted stars.

Accordingly, constant attempts are being made to reduce atoms to
one simple element, and to one comprehensive law. The problem is not
yet solved ; but it is being attacked on various sides, and almost every
day brings us nearer towards a solution. Hydrogen first put in a claim
to be the primitive element, as being the lightest, and it is remarkable
that the weight of a very large proportion of the other elementary atoms
is an exact multiple of that of the hydrogen atom. The spectral lines of
hydrogen are also the last seen in those of the hottest stars, where all sec-
ondary combinations may be supposed to be dissociated. This hydrogen
theory, which was first proposed by Prout, can hardly be said to be firmly
established, as there are some important elements, such as chlorine and
sodium, which do not correspond with the law of being simple multiples
of hydrogen. Still the agreement is too close in a number of cases to be
accidental, and the latest researches show that by halving the hydrogen
atom, that is, supposing this atom to be composed of two-linked atoms,
the deviations from the law may be reduced within limits which may be
fairly attributable to errors in the delicate operations requisite for
fixing atomic weights. Mr. Crookes suggests that helium, which is
only known from a single 3jne in the solar spectrum, and which
is apparently lighter than hydrogen, may be this half-hydrogen-atom,
and thus be the ultimate element out of which all other atoms
are manufactured. For Herschell and Clark Maxwell both arrived at
the conclusion that "atoms bear the impress of being manufactured
articles."

It is, in fact, certain that some relation exists among them, for the
Russian chemist Mendelejeff has shown that if the atomic weights of the
known elements are arranged in a consecutive order, they show what is
called a periodical law. That is, the other qualities of atoms, such as
specific heat, affinity, atomicity, etc., rise with the weights up to a
certain point, then fall, then rise again, and so describe a sort of zig-
zag line like those we see of the readings of the barometer on a weather
chart. Only this atomic zig-zag seems to follow a certain law, so that
groups of elements which have similar qualities recur at nearly fixed
intervals.

The meaning of this law is not yet clear, but it is so certain that it
enabled Mendelejeff to predict the discovery of three new elements which
have since been found, filling up gaps in the series which his law
required.

The nearest approach to a mathematical explanation of this law is
afforded by the discovery that if the cube roots of the atomic weight*
were used as ordinates instead of the weights themselves, which i
equivalent to taking volumes instead of lines to represent the atomic
weights, the zig-zag line resolves itself into a regular curve, which is



32 BEACON LIGHTS OF SCIENCE.

identical with, or very closely resembles, the logarithmic curve well known
to mathematicians.

What the effect of these laws may be is not yet fully known, but they
all point towards the conclusion that the atoms which we call elementary
are all really manufactured out of some one atom or sub-atom, which is
the primary element of matter. Where are they manufactured ? Crookes
says on the outside of the universe, wherever that may be, and that they
are destroyed or dissociated when they reach the position of the lowest
potential energy, which is in the centres of the largest stars. This may
or may not be true, but it shows the direction in which speculation is
tending, and carries our conceptions of the possibilities of the universe far
beyond the limits of the nebular hypothesis and the results of the law of
gravity.

This also may be said of the atoms, whatever sort of manufactured
articles they may be, they are manufactured to the same pattern, like
the nuts and screws of a large locomotive or gun factory. The hydro-
gen-atom gives the same spectral lines, which means that it vibrates,
and starts or absorbs ether-waves precisely in the same manner, whether
it exists in Sirius, in the nebula of Orion, or in a jar of gas in a
laboratory.

The problem of atoms is being attacked from another side. What,
after all, are atoms, or the primary protyle or sub-atom, if we can succeed
in tracing them back to one origin? The general idea is that of an
almost infinitesimally small, but still finite, unit of matter, impenetrable,
indivisible, and endowed with enormous energies, both of velocity and
attractive and repulsive forces. Various other ideas have been started.
Some have considered them as mere centres of force without parts or
magnitude; others as condensed portions of a continuous matter; but all
these theories are open to fatal objections, and the conception of atoms
has pretty well settled down to that of small separate bodies floating like
buoys, in an ocean of ether, that is, of the still rarer, all-prevading medium
which transmits light and heat. This accounts best for all the phenomena
hitherto observed, and may be said to hold the field. The only serious
competitor with it is the vortex theory of Helmholtz and Thomson, which
assumes atoms to be revolving rings of a perfect fluid pervading space.
The general idea is given by the rings of smoke which occasionally es-
cape from the lips of smokers. These rings persist for a long time, glide
before the knife so as to be indivisible, and when two of them collide they
rebound and vibrate. In a word, they behave in many respects very like
atoms, and refined mathematical calculations show that if we could sup-
pose them formed and rotating, not in air, but in what is called a perfect
fluid, incompressible, possessing inertia, and yet offering no resistance
whatever to motion through it in any direction, such vortex-rings would
be indeed indivisible and indestructible, and might well be what we call
atoms. The theory is extremely ingenious, 1 ut it has hardly yet got be-



PROBLEMS OF THE FUTURE. 33

yond the stage of a mathematical speculation, like space of four dimen-
sions, which has no relation to actual facts known by observation and
experiment.

To begin with, there is absolutely no proof of such a medium as is
required. It is already difficult enough to realize the conception of such
a medium as ether, though its waves can be measured, and its existence
is imperatively demanded by the phenomena of light and heat. But to
suppose a second and equally all-pervading medium, of a different nature,
and with properties still more inconceivable, is too much for the imagina-
tion, and would require to be supported by undoubted facts. Again,
atoms have weight, and the supposed medium has no weight and offers
no resistance. Why should a portion of it acquire weight by being made
to rotate ; and what conceivable cause could set it rotating ? But the
most fatal objection is, how could such rings continue to rotate unless
some external or centripetal force counteracted the centrifugal tendency
to fly off from the circumference in a straight line ? Rotation implies
centrifugal force, and matter which possesses inertia and obeys the first
law of motion must inevitably fly off, unless acted on by some other force.
In the case of the earth, the sun's attraction supplies the centripetal force ;
in the case of a wheel or bicycle the molecular cohesion of the solid parts ;
in the case of smoke-rings the resistance of the air. But what supplies it
in the vortex-rings, rotating in a perfect fluid, which offers no resistance
to any motion ?

It will be seen that the problem of atoms, involving that of the ulti-
mate constitution of matter, is fast advancing towards some definite solu-
tion ; but it is not yet solved, and is a problem of the future. Seeing,
however, the wonderful advances which have been made in the last half-
century, and specially in the last few years, it is impossible to doubt that,
as in the case of gravity, some future Newton will sum up in some com-
prehensive law all the scattered facts which point in the same direction
towards the unity of the universe, and the persistence of evolution from
the simplest to the most complex.

But even when this triumph of science has been attained, the question
remains as insoluble as ever Whence came this primeval matter and pri-
meval energy ?

I recollect as a boy looking up at the stars, and asking myself what
does all this mean ? Where did it come from, and what is beyond it ?
The only answer was a sort of painful ache, as of straining the eyes to see
in the darkness. And now that, thanks to the discoveries of modern
science, I can see so much beyond the visible stars, far off into the infi-
nitely great, far down into the infinitely small, far back into infinite Time
at the end of all I am not one whit advanced beyond that feeling of
boyhood. I gaze with straining eyes into the Unknowable, and gaze in
vain. Others may see, or fancy they see, something behind the knowable
phenomena of the universe, linked together by invariable laws. Some a



34 BEACON LIGHTS OF SCIENCE.

personal God, others a design like human design, a living whole, ideas in
a Universal Mind, illusion, Maya Nirvana, what not. For my own part,
if I candidly confess the truth to myself, I can only say with Tennyson

"Behold! I know not anything,"

and content myself with the only creed which seems to me certain, that
of trying to do some little good in my generation, and leave the world a
little better rather than a little woise lot tuy individual unit of existence.



CHAPTER III.
CUMATE.

GEOLOGY and astronomy are in conflict on other questions as well
as that of the time during which a sufficient supply of solar heat
has rendered the earth habitable. The conditions of that supply are as
important as the total quantity, and these conditions depend mainly on
climate. Geology seems to show that during the vast lapse of time em-
braced by fossil records from the Cambrian to the close of the Tertiary
period, there were no well-marked zones of climate, and the conditions
of life were uniform, or nearly so, throughout the whole earth. Astron-
omy, on the other hand, asserts that the vicissitudes of the seasons, with
their corresponding zones of climate, must have existed from the begin-
ning as they now are. Geology relies on undoubted facts. Coral forma-
tions, which require both a warm and an equable climate, and cannot
live in a temperature below 66 Fahrenheit, were found by Captain Nares
in Greenland, in latitude 8 1 40'. Ammonites of the same genera and
even of the same species are found alike in Melville's Island and in India ;
and Ichthyosauri have been met with in Greenland and Spitzbergen.
Lyell, Dana, and all modern geologists agree that in primordial times
there were " no zones of climate," " no marked difference between life in
warm and cold latitudes ; " " warm Arctic seas all the year round."

This continued until what is, geologically speaking, quite the other
day, the close of the Tertiary period. In Spitzbergen, latitude 78 56',
are found the remains of a luxuriant Miocene flora, comprising species
like the common cypress, which now grow in the Southern United States
and California. Magnolias and zamias are found in Miocene strata in
Greenland in latitude 70.

These species, it must be observed, require not only a warm but an
equable climate. They would be killed by a single severe night's frost,
and yet they grew and flourished where the winter night now lasts for four
months, and where the thermometer has registered more than 100 below
freezing-point. The difference between summer and winter temperature
in high Arctic latitudes exceeds 100 Fahrenheit, and whatever may have
been the initial temperature, this difference of heat, due to solar radiation,
must have been added and subtracted every year, as long as the earth's
axis of rotation preserved its present obliquity to the plane of the ecliptic

35



j6 BEACON LIGHTS OF SCIENCE.

in which the earth revolves round the sun. If the temperature of Spitz-
bergen was from any cause high enough to prevent the thermometer from
falling below zero in winter, it must have risen in summer far above the
extremest tropical temperature at which life and vegetation are possible.

Nor is it a question of temperature only, but of light and the actinic
rays of the solar beam, which are equally essential for vegetation. A lux-
uriant forest vegetation, including such forms as the magnolia and cypress,
could no more flourish under any conditions now known to us in Spitz-
bergen, than they could if shut up for four months in a dark cellar. And



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